This invention relates, generally, to the production of thin films and, more particularly, to a semiautomatic apparatus for cutting and diverting a continuously advancing, freshly cast web without loss of web-forwarding tension.
In existing machines, film is produced by extruding a web of molten, polymeric, film-forming materials onto a quench wheel and then advancing the web through stretching and slitting stations to one or more windups. During startup, the cast, unoriented web is led manually under the quench wheel and over rolls located adjacent the quench wheel. From those rolls, it is guided through a slot in the floor to a waste accumulator. After the desired cast profile has been achieved, a manual traversing knife is inserted through the web adjacent one of its sides to form a strip which is then cut to form a leader. When that leader has been threaded through the stretching stations to another waste collector, the traversing knife is moved across the web, thereby transferring it to the production thread-path. Next, the stretched, oriented film is routed through the slitting station to the windups. For planned stoppages at or beyond the stretching stations, the quenched web can be re-routed to the waste accumulator by first cutting a leader, guiding it to waste and then traversing the knife through the web. In the event of an unplanned stoppage, an operator uses scissors to cut a leading edge across the tough, thick, unoriented, amorphous, cast web and then must manipulate that leading edge through the slot to the waste accumulator. Forwarding tension is lost when the web is cut. The time required to accomplish this operation safely places a limit on the maximum throughput for the entire machine.